Although psoriatic arthritis (PsA) affects up to one million Americans, obtaining a diagnosis can be difficult. There are no tests to accurately determine its presence, and it can mimic other conditions which can also result in painful inflammation and swelling of the joints. To make a diagnosis, doctors, usually rheumatologists, use a process of elimination which involves a series of tests, clinical observations and information gleaned from patients. The correct diagnosis is crucial because it is the only way to ensure that patients receive appropriate treatment.
Since psoriatic arthritis is similar to other chronic, inflammatory conditions such as gout, osteoarthritis and rheumatoid arthritis, several different tests are used to rule them out. For example, gout occurs when a normal waste product called uric acid causes a build up of crystal deposits in the joints. Rheumatoid arthritis is similarly confused with psoriatic arthritis, but it is almost always associated with the presence of a protein called rheumatoid factor, which is found in patients with rheumatoid arthritis but is usually not present in people with psoriatic arthritis.
To detect inflammation, doctors often use a test that checks the erythrocyte sedimentation rate, or sed rate, in the blood. This is done by measuring the degree of rapidity with which red blood cells sink in a specimen of drawn blood.
Copyright 2009 NBC Health
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